Various emulsions are known in the art to be difficult to separate. For example, crude oil sometimes contains varying amounts of emulsified water which must be removed before further processing thereof. Because of the surface activity and the high viscosity of said crude oil, it is very difficult to break these emulsions to remove the water. Various methods have been tried, including heating, electrostatic precipitation, filtration, coalescense, addition of solvents and diluents, and centrifugation. In U.S. Pat. No. 1,472,384, a process for the demulsification of crude oil is disclosed, which relies on the use of a solvent which is miscible with water and to an extent the oil. The patentee discloses that methanol, ethanol and acetone may be used as the solvent. In one embodiment of the invention, the patentee treats his separated oil after the demulsification process by heating to remove the dissolved solvent and also various lighter hydrocarbons which he returns for use in demulsification of other crude oil emulsions. The patentee notes that the lighter hydrocarbons in admixture with his solvent formed an improved demulsification mixture since said lighter hydrocarbons increased the fluidity of the crude oil. The instant invention differs from this process in the following ways.
While patentee recognized that a mixture of (alcohol or ketone) solvent and light hydrocarbon formed an improved demulsification mixture, he utilized only light hydrocarbons present in his emulsion feed for this purpose. By vaporization, condensation and recycle, he was able to build up the amount of light hydrocarbon in his demulsification mixture to a desired, though unspecified amount.
This technique introduces very undesirable separation problems into the steps following the emulsion breakage, namely, the distillation operations wherein the demulsification mixture of solvent and hydrocarbon are recovered. The oxygenated solvents and light hydrocarbons used by the patentee form azeotropes with each other and ternary azeotropes with water, so that the final separation of demulsification mixture and separated emulsion becomes difficult and expensive.
In order to avoid this difficulty, and further to increase the flexibility of choosing preferred components for the demulsification mixture, it is important to employ constituents in the demulsification mixture which boil far enough below the nonaqueous constituents of the emulsion to be broken, so that there is no fractionation problem and no tendency to form azeotropes. Consequently, preferred light hydrocarbons and alcohols can be employed singly or in combination to break the emulsion without incurring a prohibitive process debit to separate this demulsification solvent from the product oil or water phase.
Finally, the patentee worked with crude oil emulsions and thus did not discuss the demulsification of oil in water emulsions.
In U.S. Pat. No. 2,287,567, a mixture of naphthalene and carbolic acid dissolved in kerosene or stove oil is taught for use in demulsifying crude oil emulsions. U.S. Pat. No. 1,980,118 teaches the use of water insoluble alcohols for the same purpose.
Water-in-oil emulsions occur during the use of various lubricating oils. U.S. Pat. No. 2,376,418 teaches the addition of isopropanol in a light bodied mineral oil or benzol carrier to a lubricating oil to promote the agglomeration of emulsified water. The teachings of this reference differ from the process of the instant invention in one important aspect. Because of the low amounts of water likely to be emulsified in the lubricating oil, the patentee needs as little as a half percent isopropanol to cause agglomeration. Furthermore, the patentee because his process includes a filtration step does not need nor does he recognize the importance of using larger amounts of isopropanol to effect rapid demulsification, i.e., the separation of the water-in-oil emulsion into separate layers.
Other references which disclose the use of a solvent to break water-in-oil emulsions include U.S. Pat. No. 2,036,299 wherein a C.sub.4 to C.sub.8 alcohol is used to break emulsions of dilute sludge acids which results from the refining of lube oils with sulfuric acid, and U.S. Pat. No. 2,270,837 which relates to the use of isopropanol and water to break Stoddard's solvent emulsions.